On the Structure and Affinities of Palaeodiscus and Agelacrinus . show no trace of median suture orpore, figs. 10,11. They do not correspond in number to the side coveringplates, but are somewhat larger, figs. 10,11. Jaekel (8, p. 17) has the same 1904.] Affinities of PalmoMscus and Agelacrinus. •observation with regard to the flooring plates of Hemicystis. ^ Deren Zahlnicht immer genau so gross ist wie die Zahl der Saumplattchen, so dasswohl bisweilen je 2 auf einer solchen Subambulacral-Platte aufsitzen,I can find no correspondence in number between the side-covering andthe flooring plates.
On the Structure and Affinities of Palaeodiscus and Agelacrinus . show no trace of median suture orpore, figs. 10,11. They do not correspond in number to the side coveringplates, but are somewhat larger, figs. 10,11. Jaekel (8, p. 17) has the same 1904.] Affinities of PalmoMscus and Agelacrinus. •observation with regard to the flooring plates of Hemicystis. ^ Deren Zahlnicht immer genau so gross ist wie die Zahl der Saumplattchen, so dasswohl bisweilen je 2 auf einer solchen Subambulacral-Platte aufsitzen,I can find no correspondence in number between the side-covering andthe flooring plates. At times, two side covering plates appear to reston one flooring plate on one side of the groove, figs. 10, 11, but, on theother side, the corresponding plates lie on portions of more than oneflooring plate. This may be due, however, to secondary distortion. The above account of the structure of the ambulacral groove is<jonfirmed by a study of a specimen of Agelacrinus cincinnatiensis, inwhich the side-covering plates have been dissolved away along most of. Eia. 10.—View i mm* removed or 20 sections -^^ mm. thick. the ambulacra. The flooring plates, which agree precisely with thoseof have been thus exposed. They show grooves along theirborder, which are the articulation of the upper series, Plate 1, fig. 2. The flooring plates enclose the mouth, except in the anal inter-radius. In the ground specimen of A, ])ileiis they have been slightlydisplaced. They are more naturally preserved in the A. cincinnatiensisexamined, Plate 1, fig. 2. The fact that the flooring plates do notenclose the mouth in the anal inter-radius is a necessary consequence ofenlargement of this inter-radius. The plates of the mouth are merelythe flooring plates of the ambulacra. The ambulacra I and V do notmeet in the angle of the anal inter-radius, and consequently the mouthring cannot be completed by these plates. The enlargement of the 42 Mr. W. K. Spencer. On the Structure and [Mar. 22, an
Size: 1814px × 1378px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1900, booksubjectproceed, bookyear1904
